A sticky story

There is, today, an infectious fungus spreading throughout most screen-printing shops. At first look it is only visible in the immediate area around the press where it takes on the form of a soft furry coating, infiltrating every nook and cranny of your press. Before long, it has spread to the dryer and then very quickly makes its way onto the walls and floors, infecting the light fixtures and ceiling on the way. What is this strange ‘Star Trekian’ creature that is overtaking your ship, I mean shop? Is it fall-out from some secret government weapons test, or is it something closer to home?

You interview everyone in your shop. Maybe it’s coming from the art department, or the dark room, or even from the screen reclaiming area. In desperation you talk to your top man, the ‘Big Kahuna’, the ‘Squeegee Puller’… your press operator! You ask him: “Well, what do you think?” In true technical printing jargon, he replies: “Dunno boss.” As you walk away totally befuddled, you notice that inauspicious can of adhesive that he has grasped between his knees.

You watch and, in one supersonic movement, he grabs the can, sprays the pallet and returns it to his trusty knee holster. But wait – what is that fine mist that you see floating past his face? Could this be the unlikely source of this ‘bubonic’ type plague that has infected everything that you hold dear in your shop? You bet it is!

If this colourful yet dramatic narrative sounds just a little bit to familiar, then you may be suffering from what is commonly known as “glue build up @#$$”. Why does this happen? Aerosols typically use flammable gasses as propellant and these, by nature, are lighter than air. When the can is sprayed, you are relying on the force of the spray to transfer the adhesive to the pallet. In tests, only approximately 50% of the adhesive gets on the pallet. The rest simply floats away to settle where it will. When you add this sobering statistic to the inaccuracy of the person spraying, the cost of aerosol, the cost of cleaning up the over-spray, and then factor in the environmental and health implications, the long term cost of using aerosols is much higher than the simple cost per can.

What can you do? Obviously the amount of over-spray and associated problems are related directly to the amount of aerosol you are using. If you are only using a few cans per year then your over-spray problem will be minimal. If you are going through six or more cans/month then you need to make some changes in how you apply glue to the pallet. Accurate handling of the aerosol can eliminate some over-spray, as will careful masking of the floor and machine around the loading station.

The simplest way to eliminate the problems associated with aerosol adhesives is to eliminate the aerosols themselves. Alternative products do exist that will perform as well as, or even better than aerosols. There are available three basic alternatives.

1 Double sided pallet masking tape

2 Water-based direct apply spreadable adhesives

3 Water-based bulk sprayable adhesive systems.

The first, double sided tapes, similar to pallet mask tape, tend to be very expensive and do not hold up very well under long term use or flashing. For very short runs they can be useful; however, cost and longevity are a problem along with the time involved for their applications.

Direct apply adhesives can be troublesome as the dry times vary. A good tip is to apply a good base of adhesive and flash each pallet off so the adhesive is dry. Once in full swing the pallets warm up so this will help with re-application. As you print, typically less adhesive is require when re-applying. Direct apply are a mixed bag – some are very good while others offer only mediocre adhesion; the latter group also has a tendency to transfer to the garment. A good test is to see if you can roll the dried adhesive off the pallet with your finger. If you can, then you can bet that some of it will end up inside or on your shirts.

Look for high solid water-based acrylics as these will give you the thinnest layout and fastest dry times. If a solvent-based adhesive is used, you re-visit a lot of the environmental and health problems associated with aerosols. With this in mind, Tekmar manufactures a product called TB-HV that is formulated using a high solid (65%) micro-emulsion acrylic. It spreads super thin and dries in seconds. Its superior bonding virtually eliminates transfer but still allows an easy peel of the shirt.

The third alternative is by far the most desirable replacement for aerosol. There are systems available that can apply both water and solvent-based bulk adhesives directly to the pallet. Some of these are air-driven and others are airless electric. The airless units apply a very controllable spray of adhesive. However, as a result of not using air, they often have the disadvantage of applying it wet rather than dry. This delays the printing process and can cause transfer of adhesive to the shirt. This problem is far more prevalent when spraying the more desirable, water-based adhesives. Solvent based adhesives often are high in VOCs (volatile organic compounds) and, due to the nature of being lighter than air, solvents are normally flammable, once again adding to the ‘floating adhesive’ problem.

Imagine a system that could spray a long lasting, instant tacking, water-based adhesive onto the pallet with virtually no over-spray. These systems do exist and are available now from Tekmar. A spokesman for the company reports that 4.55 litres (one gallon) of its bulk water-based adhesive, replaces a minimum of six dozen (six cases) of 0.45 litre (16 ounce) cans of spray tack. The TB range of adhesive applicators is designed for all size operations, from small single manual press shop to companies running multiple automatic presses. The all water-based adhesives line includes the industry standard TB-10 for T-shirts and fleeces, TB-EZ for PPF (polyester performance fabric), a special formulation of the TB-EZ (TB-EZX) developed to meet the strict Nike protocols and TB-15 for embroidery appliqué adhesion. What makes this system unique is the utilisation of its HVLP (high volume low pressure) technology.

HVLP allows the adhesive to be applied with a large volume of air, at low pressure. This ensures that the adhesive is sufficiently dry for continuous loading of shirts, without the blast of air that would normally force adhesive all over the printing press and all over the shop.

Obviously even the most fastidious operator is still going to have some adhesive miss the pallets. For this eventuality, Tekmar has also developed the AV1. This is a compact box that sits under the unload station and has a downdraft fan that draws any errant adhesive through a replaceable filter panel so that it doesn’t end up all over the floor and base of the press. For a few dollars a week the area under your press can also be virtually adhesive free.

Tekmar has thousands of installations at work all over the globe and has become the benchmark for bulk adhesive systems. Shops using these types of systems experience faster production, cleaner premises, less adhesive left on garment and a far more environmentally friendly and safe working environment. Aerosols are old technology that no longer belongs in the screen-printing workplace. The future is water-based adhesive technology delivered in a cost effective, environmentally safe manner.